This proposal is intended to elucidate the role of cyclic AMP as a physiological mediator of hormone action using hormone induced steroidogenesis as a model system. The phosphoproteins of cultured adrenal and Leydig cells obtained from normal and tumor tissues will be labelled with radioactive phosphate. Concentrations of ACTH, hCG, and their partial agonists analogs which stimulate steroidogenesis without inducing detectable cyclic AMP accumulation will be tested for their effects on formation of radiolabelled phosphoproteins. If enhanced phosphorylation of specific proteins is detected in response to hormonal cyclic AMP stimulation, then the role of cyclic AMP as a mediator of hormone action will be supported. Conversely, if no phosphorylation is detected, the role of cyclic AMP will be suspect and alternate second messengers will have to be discovered. In addition, we propose to compare the effects of other agents such as cholera toxin and neocarzinostatin (a potent antitumor protein recently shown to increase cyclic AMP levels in lymphoma cell lines) on protein phosphorylation and steroidogenesis to those of ACTH and hCG.